(1) Field of the Invention
The present invention relates to a pressure-fixing toner for the electrophotography and a process for the preparation thereof. More particularly, the present invention relates to a pressure-fixing toner for the electrophotography, which has excellent pressure-fixing property and electroscopic property in combination, and also to a process for the preparation of this toner.
(2) Description of the Prior Art
As the conventional pressure-fixing toner, there has been widely used a toner comprising a soft fixing component such as a wax and a hard fixing component as a wax in combination as the fixing component. These soft and hard components differ greatly from each other in the softening or melting conditions and also in the properties in the molten state (for example, when a wax is molten, a liquid having a low viscosity is formed). Accordingly, the operation of kneading the soft and hard components is very difficult.
For this reason, a pressure-fixing toner comprising such soft and hard components is mainly prepared according to a spray granulation method or the like. For example, the specification of U.S. Pat. No. 4,016,099 teaches the preparation of a microencapsulated toner by using a hard component as the shell and a soft component as the core. Furthermore, Japanese Patent Application Laid-Open Specification No. 119928/79 discloses a multinuclear microencapsulated toner comprising a dispersion of a soft component of the emulsion particle size in a continuous phase of a hard component.
However, in a pressure-fixing toner prepared according to the above-mentioned spray granulation method, bad influences of the solvent left in toner particles cannot be neglected, and blocking of the toner particles is readily caused in a development apparatus. Furthermore, toner particles obtained according to the spray granulation method have a substantially spherical shape, and therefore, when the toner is used as an electrically insulating toner, the charge quantity of the toner particles is inevitably smaller than that of angular particles having an indeterminate shape, though no particular disadvantage arises when the toner is used as an electroconductive developer.
In view of the foregoing, it is necessary to prepare a pressure-fixing toner excellent in both the pressure-fixing property and the electroscopic property in the form of toner particles having an indeterminate shape through kneading, pulverization and classification.